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Subject: Re: [OMPI users] How to specify hosts for MPI_Comm_spawn
From: Ralph Castain (rhc_at_[hidden])
Date: 2008-07-29 13:24:52


For the 1.2 release, I believe you will find the enviro param is
OMPI_MCA_rds_hostfile_path - you can check that with "ompi_info".

On Jul 29, 2008, at 11:10 AM, Mark Borgerding wrote:

> Umm ... what -hostfile file?
>
> I am not starting anything via mpiexec/orterun so there is no "-
> hostfile" argument AFAIK.
> Is there some other way to communicate this? An environment variable
> or mca param?
>
>
> -- Mark
>
>
> Ralph Castain wrote:
>> Are the hosts where you want the children to go in your -hostfile
>> file? All of the hosts you intend to use have to be in that file,
>> even if they don't get used until the comm_spawn.
>>
>>
>> On Jul 29, 2008, at 9:08 AM, Mark Borgerding wrote:
>>
>>> I've tried lots of different values for the "host" key in the info
>>> handle.
>>> I've tried hardcoding the hostname+ip entries in the /etc/hosts
>>> file -- no luck. I cannot get my MPI_Comm_spawn children to go
>>> anywhere else on the network.
>>>
>>> mpiexec can start groups on the other machines just fine. It seems
>>> like there is some initialization that is done by orterun but not
>>> by MPI_Comm_spawn.
>>>
>>> Is there a document that describes how the default process
>>> management works?
>>> I do not have infiniband, myrinet or any specialized rte, just ssh.
>>> All the machines are CentOS 5.2 (openmpi 1.2.5)
>>>
>>>
>>> -- Mark
>>>
>>> Ralph Castain wrote:
>>>> The string "localhost" may not be recognized in the 1.2 series
>>>> for comm_spawn. Do a "hostname" and use that string instead -
>>>> should work.
>>>>
>>>> Ralph
>>>>
>>>> On Jul 28, 2008, at 10:38 AM, Mark Borgerding wrote:
>>>>
>>>>> When I add the info parameter in MPI_Comm_spawn, I get the error
>>>>> "Some of the requested hosts are not included in the current
>>>>> allocation for the application:
>>>>> [...]
>>>>> Verify that you have mapped the allocated resources properly
>>>>> using the
>>>>> --host specification."
>>>>>
>>>>> Here is a snippet of my code that causes the error:
>>>>>
>>>>> MPI_Info info;
>>>>> MPI_Info_create( &info );
>>>>> MPI_Info_set(info,"host","localhost");
>>>>> MPI_Comm_spawn( cmd , MPI_ARGV_NULL , nkids , info , 0 ,
>>>>> MPI_COMM_SELF , &kid , errs );
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Mark Borgerding wrote:
>>>>>> Thanks, I don't know how I missed that. Perhaps I got thrown
>>>>>> off by
>>>>>> "Portable programs not requiring detailed control over process
>>>>>> locations should use MPI_INFO_NULL."
>>>>>>
>>>>>> If there were a computing equivalent of Maslow's Hierarchy of
>>>>>> Needs, functioning would be more fundamental than portability :)
>>>>>>
>>>>>> -- Mark
>>>>>>
>>>>>>
>>>>>> Ralph Castain wrote:
>>>>>>> Take a look at the man page for MPI_Comm_spawn. It should
>>>>>>> explain that you need to create an MPI_Info key that has the
>>>>>>> key of "host" and a value that contains a comma-delimited list
>>>>>>> of hosts to be used for the child processes.
>>>>>>>
>>>>>>> Hope that helps
>>>>>>> Ralph
>>>>>>>
>>>>>>> On Jul 28, 2008, at 8:54 AM, Mark Borgerding wrote:
>>>>>>>
>>>>>>>> How does openmpi decide which hosts are used with
>>>>>>>> MPI_Comm_spawn? All the docs I've found talk about specifying
>>>>>>>> hosts on the mpiexec/mpirun command and so are not applicable.
>>>>>>>> I am unable to spawn on anything but localhost (which makes
>>>>>>>> for a pretty uninteresting cluster).
>>>>>>>>
>>>>>>>> When I run
>>>>>>>> ompi_info --param rds hostfile
>>>>>>>> It reports MCA rds: parameter
>>>>>>>> "rds_hostfile_path" (current value: "/usr/lib/openmpi/1.2.5-
>>>>>>>> gcc/etc/openmpi-default-hostfile")
>>>>>>>> I tried changing that file but it has no effect.
>>>>>>>>
>>>>>>>>
>>>>>>>> I am using
>>>>>>>> openmpi 1.2.5
>>>>>>>> CentOS 5.2
>>>>>>>> ethernet TCP
>>>>>>>>
>>>>>>>>
>>>>>>>> -- Mark
>>>>>>>> _______________________________________________
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>>>>>>>> users_at_[hidden]
>>>>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Mark Borgerding
>>>>> 3dB Labs, Inc
>>>>> Innovate. Develop. Deliver.
>>>>>
>>>>> _______________________________________________
>>>>> users mailing list
>>>>> users_at_[hidden]
>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>>
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